In a wireless communications system, a user acquires a certain uplink resource and a transmission mode through uplink scheduling by a base station, so as to transmit uplink data. A result of the uplink scheduling by the base station for the user depends on various factors. In addition to a result of measurement on a user's uplink channel by the base station and power information of the user, the base station further needs to acquire information about data size to be sent on a user side.
For example, BSR (Buffer State Report, buffer state report) information of the user is reported to the base station by using an MAC (Media Access Control, media access control) CE (Control Element, control element). Specifically, at an MAC layer, logic channel data and an MAC CE form an MAC PDU (Protocol Data Unit, protocol data unit), which is reported to the base station.
However, in a case in which multiple MAC PDUs are transmitted at the same time, the BSR information is transmitted to the base station in at most only one MAC PDU. When a newly transmitted MAC PDU and a retransmitted MAC PDU are transmitted at the same time, previous BSR information of the user is always retransmitted in the retransmitted MAC PDU. As a result, the base station cannot acquire current BSR information of the user for a long time, thereby affecting the uplink scheduling for the user.